Apparatus and method for forming juxtaposed as well as superimposed coatings



May 15, 1956 P. K. WEIMER 2,745,773

APPARATUS AND METHOD FOR FORMING JUXTAPOSED AS WELL AS SUPERIMPOSEDcommas 5 Sheets-Sheet 1 Filed March 25, 1956 a a a j M M M WW 0F 3 a r 0u 1 3 s n.

4 a 3 F y INVENIOR. Pau/ K. We/mer ATTORNEY May 15, 1956 P K. WEIMER2,745,773

APPARATUS AND METHOD FOR FORMING JUXTAPOSED AS WELL AS SUPERIMPOSEDCOATINGS Filed March 25, 1953 5 Sheets-Sheet 2 mumuum J/ I INVENTOR.

Pau/ Kv We/mer 11 TTOR NE 1 May 15, 1956 R WEEMER 2,745,773

APPARATUS AND METHOD FOR FORMING JUXTAPOSED AS WELL AS SUPERIMPOSEDCOATINGS Filed March 25, 1953 5 Sheets-Sheet 3 INIE .\'TOR.

Pau/ K. We/m 9/ TTORNEY P. K. WEIMER May 15, 1956 APPARATUS AND METHODFOR FORMING JUXTAPOSED AS WELL AS SUPERIMPOSED COATINGS 5 Sheets-Sheet 4Filed March 25, 1953 M e W k m P y 5, 1956 P. K. WEIMER 2,745,773

APPARATUS AND METHOD FOR FORMING JUXTAPOSED As WELL AS SUPERIMPOSEDCOATINGS Filed March 25, 1953 5 Sheets-Sheet 5 INVENTOR.

Pau/ K. We/mer Baal/1 United States Patent APPARATUS AND METHGD FORFBRMING 3U;- TAPOSED AS WELL AS SUPERIMPOSED CGAT- INGS Paul K. Weimer,Princeton, N. 3., assignor to Radio Cor poration of America, acorporation oi Delaware Application March 25, 1953, Serial No. 344,498

18 Claims. (Cl. 117-212) This invention relates to a method andapparatus for making fine, juxtaposed lines or strips of materialsparticularly useful in making ray sensitive targets for cathode raycolor television tubes. More particularly this invention relates to amethod and apparatus for evaporating materials to form targets havingsignal strips and/ or color filter strips especially useful insimultaneous color television pickup tubes.

The methods and apparatus heretofore proposed for making fine,juxtaposed strips which are extremely thin in cross section haverequired repeated handling of the work by highly skilled operators aswell as being time consuming without attaining the high degree ofprecision desired.

it is, therefore, a principal object of my invention to provide animproved method and apparatus for making fine juxtaposed as well assuperimposed strips which are extremely thin.

Another object is to provide a highly advantageous method and apparatusfor making an article such as a target for a color television pickuptube and having juxtaposed strips made up of one or more layers ofextremely thin precisely determined cross sectional thickness.

Yet another object is to provide an improved method for making colorfilter strips each composed of a plurality of layers and having adesired eificiency.

Still another object is the provision of apparatus for readily makingnarrow, thin strips in accurate juxtaposed relation which strips areformed in a controlled atmosphere and each may differ from the stripadjacent thereto.

A further object is to provide apparatus which facilitates the making ofnarrow, thin strips in accurate juxtaposed relation whereby adjacentstrips are formed successively without requiring removal of the workfrom the apparatus or manual handling thereof.

In accordance with my invention 1 provide a movable workpiece holderwhich permits ready precise location of the workpiece on one side of afixed mask having alined apertures. The holder is readily displaced in agiven direction to expose difierent portions of the workpiece to theapertures of the fixed mask. On the other side of the fixed mask, amovable mask is mounted which determines the length of the apertures inthe fixed mask in a transverse direction to the aforementioned givendirection as well as effectively shifting the apertures of the fixedmask in the transverse direction with respect to the workpiece. Acontrolled atmosphere may be provided in a chamber in which theapparatus is mounted and the various movements of the work iece andmovable mask are effected by controls mounted externally of the chamber;thus eliminating the necessity for disturbing the atmosphere of thechamber. Various materials to be evaporated onto the surface of theworkpiece to form the strips are each located in the chamber so that thedesired material and in the proper sequence may be evaporated throughthe masks onto the workpiece. The workpiece being transparent, thethickness of the various layers is accurately 2,745,773 Patented May 15,1956 controlled by passing light through the workpiece and measuring thelight transmitted.

Further objects as well as advantages of my invention will be apparentfrom the following description and the accompanying drawing in whichFigure l is an elevational view, partly in section of apparatusconstructed in accordance with my invention;

Figure 2 is a plan View, broken away and on an exaggerated scale, of onetype of article particularly suited for manufacture in accordance withmy invention;

Figure 3 is a sectional view along the line 3-3 of Figure 2 on anenlarged scale;

Figure 4 is an enlarged fragmentary sectional view of one of the colorfilter strips not drawn to scale and showing the various layers;

Figure 5 is a perspective view, partially broken away for convenience ofillustration, of a jig constructed in accordance with my invention;

Figure 6 is a sectional view along the line 6-6 of Figure 5;

Figure 7 is an exploded view of various parts of the jig and aworkpiece;

Figure 8 is a fragmentary sectional view along the line fi$ of Figure 5;

Figure 9 is a fragmentary sectional view of another portion of the jig;

Figure 10 is a sectional view of one type of mask; and

Figure 11 is a perspective view of another type of mask.

Referring now to the drawing and to Figure l in particular it is seenthat the apparatus includes a jig 10 supported in abell 11 above anevaporator 12. The interior of bell i1 is connected, in the presentinstance, to a vacuum pump (not shown).

it may be well to state here that in the present illustrativedisclosure, the apparatus is shown as employed for making one form oftarget for a color television pickup tube. While my invention findsparticular applicability to this use, it is to be understood that thepresent disclosure is by way of exemplification only. In the presentinstance, the apparatus is constructed for making such targets whichwill presently be more fully described. it is, of course, obvious thatthe apparatus as well as the method to be described herein may beemployed to make articles other than the type here described.

It is believed that my invention will be most readily understood byfirst referring to one form of target for a simultaneous colortelevision pickup tube in connection with which my invention isparticularly useful. Such a target is described in detail in myapplication, Serial No. 344,497, filed simultaneously herewith andassigned to the assignee of this application. Referring then to Figures2, 3 and 4, target 20 is shown with the dimensions thereof grosslyexaggerated to facilitate this description. Target 29 comprises asupport or workpiece 21 of clear glass having three spaced conductivelines or bus bars 22 adjacent opposite ends thereof. Extending acrossthe surface of workpiece 21 are a plurality of juxtaposed color filterstrips 23. As will be more fully described the filters are of theinterference type and may include filters for the primary colors red,green and blue. Color filter strips 23 are in practice quite narrow asfor example about .002 inch wide. Strips 23 are shown in side by sideabutting relation, however, as will be apparent, they may be readilymade so as to be juxtaposed in close spaced apart relation. The colorfilters 23 of the same color are alined with respect to each other butofiset longitudinally with respect to the filters of the other colors asshown.

Transparent conductive signal strips 24 are formed one on each of thefilter strips 23. Signal strips 24 are each somewhat longer than filterstrips 23 and are oflset with respect to each other as described inconnection with the filter strips. When filter strips 23 are in abuttingrelation, as shown, signal strips 23 are somewhat narrower than thefilter strips and, as for example, are .0015 inch wide. Signal strips 24on the red filters are connected adjacent each end thereof to red busoars 22 and thus form a set of red signal strips. Similarly, signalstrips 24 on the green and blue filter strips are each connectedrespectively to the green and blue bus bars. It is apparent then thatthree mutually independent sets of signal strips each interlaced withthe other are provided.

As most clearly shown in Figure 3, filter strips 23, which are ofinsulating material, serve to insulate signal strips 24 from the busbars 22 of the other colors at the points Where the signal strips forone color cross the bus bars for another color. For example at thepoints where a red signal strip crosses over the blue and green hasbars. When desired, additional material, such one of the materialsforming filter strips 23, be previously applied at those crossoverpoints, shown as a separate layer 23' for convenience of illustration,to provide added insulation. Where signal strips 24* make electricalconnection to their respective bus bars an intermediate conductive layeror finger strip 25 may be formed (Figure 3) when additional capacitanceis desired. Such finger strips are described in detail in theapplication Serial No. 344,616 of S. Gray filed simultaneously herewithand assigned to the assignee of this application.

Each of the color filter strips is made up of a number of successivelysuperimposed layers. Red and blue filters are made from elevensuccessive layers of zinc sulfide and cryolite as shown in Figure 4.Similarly, successive superimposed layers of zinc selenide and cryolitear ut ized, but only nine in number, to form green filters.

Referring now to Figures 5, 6 and 7, jig ll? is conveniently supportedin bell 11 on platform 3% having an opening 31 formed therethrough. Figll comprises two major subassernblies which are readily disconnected andconnected again in accurately alined relation. The base or masksubassembly includes fixed mask 32 and movable mask 33 mounted on base34. The workpiece subassembly includes a supporting framework 69 havingworkpiece holder 61 movably mounted therein. Means for accuratelylocating workpiece holder 61 with respect to masks 32 and 33 areprovided.

On the upwardly presented surface of base 34-, a pair of oppositelydisposed guide rails 28, 29 (Figure 5) form a guideway which movablemask 33 is slideably mounted. Means for accurately and adiustablypositioning movable mask 33 are provided by means of which both a largeand fine adiustment of movable mask 33 may be readily made. Movable mask33 may be reciprocated in the guideway on base 34 by rotatably mountedarm 35, a finger portion 35 of which engages movable mask 33. in thepresent instance finger portion 35' conveniently extends into slot 36formed in movable mask 33 adjacent to one end thereof. As shown inFigure 5, arm 35 is supported on and is rotatable with rod 37. As willbe hereinafter more fully described, rod 37 is connected through asuitable seal and gear train to a control knob located externally ofbell it thus permitting ready adjustment thereof without disturbing bell11 or its contents. A precise, micrometer adjustment for movable mask 33is provided in the form of rod 38 rotatably mounted in base 34. One endportion of rod 38 is threaded into base 34 as at 39 while a beveled gear40 is mounted on the opposite end portion thereof. Rod 38 is rotatablewith gear 40 which is in turn driven by bevel gear ll rotatable with andsupported on rod 42. To permit relative movement of rod 33 with respectto gear 40, rod 38 is slideable in the hub of gear 43 and is keyedthereto by spline 43 (Figure 6). Stops in the form of collars 44, 45 aremounted in spaced rela tion on rod 38 and are engaged by a downwardlyextending projection or lug 46 on movable mask 33. Thus, the throw ofarm 35 slides movable mask 33 in its guideway to position projection 46either against stop 44 or stop Rotation of rod 38 permits selectivepositioning of mask 33 in either position as a result of the movement ofcollar 44 or 45 as the case may be. in view of the sliding engagement ofgear ll) with rod 33, resilient finger 47, conveniently mounted onplatform 30, urges gear i li toward rod 33 and against drive gear 41.

Mounted on base 34 and positioned over movable 33 is fixed mask 32.Fixed mask 32 is shown in the form or a wire masking gril having aplurality of fine closely spaced wires roughly indicated at 4-3 andsupported by two spaced cylinders 49, 50. The wire liv d rray be of anysuitable material. However, wire stretched under tension such as wireformed y of: 85% nickel and 15% chromium is particc'arly advantageous.The wire is wound on cylinders 59 in any convenient manner well known inthe grid ing art. Cylinders 45, Eli, with wires 48 connectedthereoctween, are each mounted on a frame 51 in spaced relation by boltsBolts are in threaded engagemeet with the cylinders 49, 5d and arerotatably mounted in posts on frame 51. Thus, adjustment of bolts servesto draw the associated cylinder away from its posts and thereby tensionand stretch wires 43. This serves to remove any kinks or bends remainingin the wires after their attachment to the cylinders. Since the spacesformed between the wires define narrow apertures through which materialsare to be evaporated the emoval of such kinks and bends prevents theformation of uude red irregularities in the coatings formed on theworkpiece.

it should be noted that the movement of movable 33 previously describedpermits the positioning of a esired portion thereof under the wiremasking grill or fixed mask 32. Movable mask 33 serves to define thelength of the apertures formed between the wires 43. This isaccomplished by the relatively large movement thereof when projection 45is moved from engage ment with stop 4% into engagement with stop 45.Movable mask 33 may be provided with such apertures as will facilitatethe manufacture of the articles in any given instance. As shown inFigure 7, movable mask is provided with an aperture 54 used in formingfilter strips 23 and slots 55 used in forming the conductive fingerstrips 25. Another movable mask having an aperture 54- (see Fig. 11),which, larger than aperture 54 in the direction of arrow 55, is used informing signal strips 2 Furthermore, in either position of mask 33rotation of rod 33 and the consequent movement of stops d4, 45 serves todisplace either ape ture 54 or slots 55 with respect to the workpieceand thereby effectively moves the evaporation apertures formed by masks32 and 33 with respect to the surface of the workpiece in the directionof arrow As will be seen, aperture 54 is positioned under workpiece 21when filter strips 23 are being formed. 'When the longer signal stripsare be ing formed a movable mask with a larger aperture 54' is place.Oiisetting of the different sets of color filters and the sets of signalstrips is accomplished by means of stops 4-4 and 35 as the case may be.

As indicated above workpiece holder 61 is mounted in framework 6%. Anaperture is provided in which workpiece 21 is readily removably seated.It should be noted that the spacing of the workpiece from the fixed mask32 is shown exaggerated in the drawing. In practice the spacing is madeas close as possible and just short of actual contact of the maskelements with the coatings to be formed so as to avoid damage thereto.Resilient fingers 62 together with spring loaded plungers 63 firmlymaintain workpiece 21 in position. Holder 21 is mounted in a guidewayformed in framework 6t? and is slideable in the direction indicated byarrow 64. Spring loaded plunger 65 (Figure 8) mounted in framework bearsagainst one end of holder 61 and urges the same against one end ofmicrometer screw 66 (Figure 9) supported in framework 60 opposite toplunger 65. Micrometer screw 66 carries on its other end gear 67 (Figurewhich is driven by bevel gear 68. Gear 68 is mounted on rod 69 which isrotatably mounted in a manner similar to that previously described inconnection with rods 37 and 42. This arrangement permits accuratepositioning of holder 61 to within a fraction of a mil from the outsideof bell 11. Graduated scales shown in Figure 5 permit visual inspectionfrom the outside of bell 11.

Means are also provided for alining the surface of workpiece 21 exposedto the apertures formed by the masks to insure a parallel relationshipbetween the workpiece surface and wires 48 of the fixed mask. Such meansinclude set screws 70 threaded into framework 60 and having bearingsurfaces abutting the under surface of holder 61. Spring loaded plungers71, also mounted in framework 60 are each apposed to one of the setscrews 70 and urge holder 61 thereagainst. Acting transversely ofplungers 71, plungers 72, one of which is indicated, urge holder 61against the opposite wall of the guideway in which it is mounted.

Bolts 73, of which there may be four, extend through framework 60 andthread into base 34 thereby serving to rigidly connect and aline theworkpiece holder subassembly to the mask or base subassembly. The properadjustment of set screws 70 having been made, framework 60 carrying theworkpiece may be removed from and then replaced on the base 34 inparallel alined relationship with fixed mask 32. Means are provided foraccurately alining wires 48 one to the other in precise parallelrelationship and with set screws 70 serve to provide predeterminedspacing between the workpiece 21 and mask 32. As described in detail inmy joint application with H. C. Thompson Serial No. 344,499 filedsimultaneously herewith and assigned to the assignee of thisapplication, such means may include a pair of spaced cylindrical membersadjustably mounted on framework 60. Each of the cylindrical members 74is precision threaded so as to have a precisely formed thread thereonwith the turns thereof per inch being equal in number to the number ofwires per inch carried by the fixed mask 32. Cylinders 74 are eachmounted in a yoke 75. Screws 76, threaded into yoke 75, together withthumbscrews 77 which bear against yoke 75, permit accurate adjustment ofcylinders 74 with respect to workpiece 21 in holder 61. When framework60 is mounted on base 34, cylinders 74 each with their threads engagewires 48. Wires 48 are thus spaced in a predetermined manner from eachother and from the surface of workpiece 21.

As previously indicated herein, evaporator 12 is mounted in bell 11below jig 10. Evaporator 12 is rotatably mounted on platform 80 by itsspindle 81. Spindle 81 has an elongated keyway 81 formed therein and isslideable through the hub of gear 82 which has a key formed therein.Gear 82 is rotatably mounted on platform 80 and meshes with idler gear33. Idler gear 83, in turn, meshes with drive gear 84 mounted on androtatable with rod 85. As shown, a rod 86 having a bifurcated end isrotatably mounted with the bifurcated end positioned between two spacedcollars on spindle 81. Thus rotation of rod 86 serves to raise and lowerevaporator 12.

Evaporator 12 is divided into compartments 12 for the various materialsto be successively evaporated. Positioned so as to overhang evaporator12 is a heating element 87 that has leads 88 sealed through bellsupporting base 13 as shown for one of the leads at 89. Leads 88 areconnected across a source of electrical power (not shown) through anyarrangement permitting control of the heat generated at element 87.

Means are provided which are also operable from outside of bell 11 forreadily starting and stopping the evaporation of material onto theworkpiece 21. One

convenient arrangement is in the form of a swingably' mounted flap 104mounted on and rotatable with rod 106. When flap 104 is in positionbetween jig 10 and evaporator 12 the material being evaporated isdeposited on the undersurface of the flap and does not reach theworkpiece. In practice the material in the evaporator is heated until itis being evaporated at the desired rate and then flap 104 is swung outof the way. Evaporation of material onto the workpiece is stoppedinstantly by swinging flap 104 into its shielding position. Thematerials may thus be subjected to prolonged heating and outgassingwithout any material being deposited on the workpiece.

One advantageous arrangement for effecting the desired movements withinbell 11 through rods 37, 42, 69, 85, 86 and 106 will now be described indetail in connection with rod 42. Each of the rods, and with particularreference to rod 42 as shown in Figure l, is rotatably sealed throughbase 13. Bushing 90 is threaded into base 13 against O-ring gasket 91and compresses the same. Such seals are well known and permit rotationof rod 42 which is connected to driven gear 92. Drive gear 93 carried onrod 94 meshes with gear 92. Rotation of rod 94, as by means of controlknob 95 connected thereto, thus effects the desired movement of stops44, 45.

Means for monitoring or controlling the formation of the variouscoatings includes a light source partially indicated at 96 which may beany suitable projector of white light. The light is projected throughthe wall of hell 11, which may be of clear glass, through tunnel 97 ontomirror 98 mounted in chimney or shield 99. Chimney 99 is provided tominimize the deposit of evaporated materials onto mirror 98. The lightis reflected by mirror 98 up through the masking apertures and workpiece21 to collimator 100. From collimator 100, the light travels to thephotocathode of phototube 101 indicated schematically. Phototube 101 maybe any suitable phototube but preferably a photomultiplier tube isutilized. The photocathode is connected to the negative side of a sourceelectricity, indicated generally by a battery while the anode orcollector is connected through a microamrneter 102 to the positive side.

My method as well as the operation of the apparatus for the purpose ofillustrating the same will now be described in connection with target 20shown in Figure 2. In this connection then, workpiece 21 is a sheet ofmaferial having suitable dielectric and optical properties such asglass. Bus bars 22 are formed by evaporating thereon narrow conductivefilms through a mask 105 shown in Figure 10. Bus bars 22 may be about500 angstrom units thick with the outside bus bars about ten mils wideand the inner ones about three mils wide. The bus bars in each of thetwo groups shown are spaced from each other about sixty mils. Gold is amaterial Zvhlch may be advantageously used in forming the bus ars.

Workpiece 21 is then positioned in holder 61 with the surface thereofcarrying bus bars 22 presented toward the wire masking grill 32. Holder61 is adjusted to expose only the areas on which red filter strips areto be formed to the apertures of fixed mask 32 while movable mask 33 ispositioned against stop 44 with slots 55 which are about 40 mils wide inregistration with the red bus bars 22. Bell 11 is placed in position onbase 13 and evacuated to a pressure of about 10- mm. of mercury or less.When desired, conductive finger strips of gold, silver or other suitablematerial are formed by evaporating said material; the material beingpositioned under heating element 87 which is energized as previouslyindicated. When finger strips of a thickness of about 500 angstrom unitshave been formed further evaporation is stopped.

Without disturbing bell 11, movable mask 33 is shifted by adjusting theappropriate control knob to bring aperture 54 in registration withworkpiece 21 for the formation of red color filter strips 23. Evaporator12 is rotated by its knob to bring the appropriate material underheating element 87. A suitable monitoring filter 103 is mounted in frontof collimator 100 and evaporation of the first layer of the red filterstrips is started. Suitable monitoring filters are substantiallymonochromatic, narrow pass interference filters of the type commonlyknown as Fabry-Perot filters. For monitoring the red filter strips afilter 193 is utilized having its pass band peaked in the blue portionof the spectrum as for example, 4,500 angstrorn units. The layers, ofwhich there may be eleven as indicated in Figure -l, are nowsuccessively formed one on the other; each having an optical thicknessof one quarter of the wavelength of the monitoring filter. Light fromprojector 95 passes through each of the layers as they are beingdeposited and on through collimator 109 to the photocathode of tube3101. Microammeter 102, by its fluctuation, indicates when a quarterwavelength optical thickness of a given layer has been deposited. Forexample, during the formation of the first zinc sulfide layer the meterreading decreases indicating that less light of 4500 angstroms inwavelength is reaching monitoring ter 103 to be passed on to tube it'll.It is to be understood that only light passing through the workpiece mayreach tube 101; measures being taken to attain that end as for examplethe inclination of collimator 1% which thereby excludes light fromheater element 87. When the current reading on meter 15?. reaches aminimum value, the layer has an optical thickness or" one quarter of4500 angstroms and further deposit of zinc sulfide is prevented byswinging flap 104 into place between the work piece and the evaporator.Evaporator 12 is rotated to bring suitable material of a low index ofrefraction such as cryolite into position under the heating element byadjustment of the proper control knob. When the cryolite is sutficientlyheated to be evaporating at the desired rate flap 164 is swung out ofthe way and formation of the second layer proceeds. This time thecurrent reading on meter res increases and reaches a maximum when theoptical thickness of the layer is one quarter of 4500 angstroms. Thenanother layer of zinc sulfide is formed with the minimum reading on themeter new lower than that for the first layer. The process is continuedwith each layer of zinc sulfide bringing to a new and lower minimum theamount of light of 4500 angstroms passed. Eleven layers of zinc sulfideand cryolite formed as above provide a suitable red passing filter.

By making the appropriate adjustments of the various control knobs,holder 61, movable mask 33, and evaporator 12 are successivelypositioned to form the conductive finger strips on the green bus bars,flse green filter strips, the conductive finger strips on the blue busbars and the blue filter strips. In the case of green color filterstrips 23 a monitoring filter having a narrow pass band peaked in thered portion of the spectrum at about 6500 angstroms is utilized. Inplace of zinc sulfide, zinc selenide is used and layers having anoptical thickness of three quarters of 6500 angstroms are formed asdescribed in connection with zinc sulfide. For blue filter strips 23sulfide and cryolite are used as described for the red filter strips buta monitoring filter 103 is used having a narrow pass band peaked in theyellow-green portion of the spectrum as for example a wavelength of of5,730 angstrom units.

When the sets of interlaced color filter strips have been formed, theinterior of hell 11 is brought to atmospheric pressure and opened. Thefour bolts 73 securing the workpiece subassernbly to the masksubassernbly are un- -wed and the workpiece subassembly removed. The\VZI'C masking grill 32 used in forming the filter strips is by asimilar grill having wires slightly larger in diameter so as to form theconducting signal strips narrower than the abutting color filter stripsand thus space the signal strips so adjacent ones are sufficientlyinsulated one from the other. The movable mask is also replaced 3 withone having an aperture 54' longer than aperture 54 to form the signalstrips longer than the filter strips. The workpiece subassernbly is thencarefully bolted in place once again. Bell 11 is put in place.

The conductive signal strips are formed by successively evaporatingsuitable material such as gold onto each of the color filter strips. Asmost clearly shown in Figures 2 and 3, the color filter strips of eachset are alined and extend from just short of the bus bar for that coloron one side to just short of the other bus bar for that color on theother side. The filter strips extend over the intervening bus bars ofthe other color sets. When the signal strips are being formed, as forexample, the red, only the filter strips and bus bars of that color areexposed through the apertures of the masks. As previously pointed outthe signal strips are about 1.5 mils in width. They are separated fromeach other about .5 mil and are estimated to range in thickness from 50to about 100 angstrom units. To form the green signal strips holder e3is shifted to expose the green color filter strips and the movable maskis shifted to expose the green bus bars. Similar adjustments permit theformation of the blue signal strips thus completing three sets ofinterlaced signal strips with the signal strips of a given set connectedin parallel by their bus bars and insulated from the signal strips andbus bars of the other colors. While the signal strips sets are formedthey are each monitored with the same monitoring filter 103 in place aswas described in connection with the respective color filter strips.This provides a convenient arrangement for determining the thickness ofthe signal strips while at the same time an undesired shift in the passband of the color filter strips is also detected.

A coating of photosensitive material 26 is formed on the signal strips24. At the present time photoconductive material is used having a broadspectral response similar to that of the human eye. One such mat rial isporous red antimony sulphide which is evaporated in poor vacuum, from .1to about 10 mm. of mercury, and has a mat surface. Such a material maybe laid down as a continuous coating over all of the signal stripsconfined to the area between the sets of bus bars by a suitablyapertured mask; the wire masking grill having been removed. This orother materials may also be evaporated through the wire masking grill soas to form the photoconductive coating in strips one on each of thesignal strips 24, as in the case where selectively color responsivephotosensitive materials are utilized.

Numerous variations may be made in the foregoing method and apparatus aswell as such as may be dictated by the article being produced. Where thecolor filter strips are not sufiiciently insulating they may be formedin spaced relation and evaporated through the same wire masking grill asis used in forming the signal strips In that case insulating layers 23'are formed at the cross over points of each of the signal strips withthe bus bars of the other colors. Apertures such as slots 55 areconveniently utilized as was described in connection with the formationof conductive finger strips 2. insulating layers 23 may be convenientlyformed at the cross over points even when the color filter strips areinsulating and in abutting relation (Figure 2) to minimize couplingbetween the signal strips of one color and bus bars of the other colors.

In view of the precise manner in which the workpiece may be readilyalined with the masks, precisely formed strips in accurate relation maybe made even though, during the preparation, the workpiece subassemblyis removed from the mask subassernbly. Thus, the usefulness of theapparatus is not impaired when as described one wire masking grill ischanged for another having wires of different diameter. Furthermore theease with which the various adjustments are carried out in a preciselyaccurate manner facilitates the following of any desired pattern orsequence of steps. For example, the

conductive finger strips 25 may be all formed before any of the colorfilter strips 23. All of the color filter strips 23 may be formed beforeany of the transparent conductive signal strips 24. While the apparatusminimizes the necessity of opening bell 11 to the atmosphere during theprocess, the number and quantity of the materials in evaporator 12 maybe varied as desired. For example, an evaporator having therein only thematerial, such as silver, for conductive fingers 25 may be used orheated during the formation of all the finger strips. Then an otherevaporator containing the material for the red and blue filter strips 23may be shifted into position by operation of external controls and heatapplied. On completion of the red and blue filters an evaporatorcontaining the material for the green filter strips may be mountedfollowed in turn by an evaporator containing material for signal strips24. Finally, an evaporator containing the photoconductive material maybe mounted for forming photoconductive coating 26. The separateevaporators may be readily mounted on a turret or turntable and actuatedfrom outside bell 11. Furthermore, when desired, conduction heating ofthe material to be evaporated may be utilized as in the case of suchmaterial as gold.

When it is not necessary to change fixed mask 32, as where all thesuperimposed layers are of the same width, a movable mask 58 may be usedhaving apertures 54, 54' and slots 55 formed therein. Mask 58 isslideably mounted in the guideway of base 34. The various adjustments ofmask 58 are effected by arm 35.

In accordance with well known techniques the various materials areoutgassed prior to their being evaporated to form the target.Conveniently, such outgassing is carried out in situs by prolongedheating in the evaporator at a temperature at which the material justbegins to evaporate. During such outgassing fiap 104 is in its shieldingposition.

Such a workpiece as target 20 may be subjected to such furtherprocessing as may be desired to enhance the properties thereof. Forexample baking at moderate temperatures has proven beneficial. In thecase of the gold signal strips described hereinabove baking for about anhour at a temperature ranging from about 130 C. to about 200 C. may beused.

From the foregoing it is apparent that I have provided a highly usefulapparatus and method. While I have described the same in connection withthe apparatus shown, it is believed obvious that changes and variationsmay be made therein without departing from my invention. It is intendedthat all such changes and variations as come within the scope of theappended claims be included in my invention.

What is claimed is:

1. Apparatus for forming juxtaposed coatings on a surface of aworkpiece, said apparatus comprising an enclosure, means for evaporatingcoating forming materials mounted in said enclosure, support meansmovably mounted within said enclosure for holding a workpiece inposition to receive said materials on a surface of said workpiece, meansfor moving said workpiece support means at least in one given direction,a mask defining a plurality of juxtaposed apertures supportedintermediate said evaporating means and said workpiece support means, amovably mounted mask supported intermediate said evaporator and saidworkpiece support means and having at least one aperture formed therein,at least one aperture in said movably mounted mask being in registrywith an aperture in said first mentioned mask and with said means forevaporating coating forming materials whereby the position of saidworkpiece and said movable mask defines the portion of said surface tobe exposed to said materials through said first mentioned mask, andmeans extending into said enclosure for efiecting movement of saidworkpiece support means and said movable mask.

2. Apparatus for successively forming juxtaposed as Well as superimposedlayers of difierent materials on a surface of a workpiece, saidapparatus comprising an enclosure, means for successively evaporating atleast two difierent coating forming materials mounted in said enclosure,movable support means for holding said workpiece in position to receivesaid materials on said surface of said workpiece, a mask defining aplurality of juxtaposed apertures supported intermediate saidevaporating means and said workpiece, means for successively registeringdifferent portions of said workpiece with said apertures, wherebyjuxtaposed coatings may be successively formed on said workpiece, andmeans sealed through said enclosure for selectively effectingregistration of difierent portions of said workpiece with saidapertures.

33. Apparatus for successively forming juxtaposed as well assuperimposed layers of difierent materials on a surface of a workpiece,said apparatus comprising an enclosure, means for successivelyevaporating at least two diflerent coating forming materials mounted insaid enclosure, movable supporting means holding a workpiece in positionto receive said materials on the surface thereof, a mask defining aplurality of juxtaposed apertures sup ported intermediate saidevaporating means and said workpiece, means for successively registeringdifferent portions of said workpiece with said apertures and including amovable mask having at least one aperture formed therein supportedintermediate said work iece and said evaporating means wherebyjuxtaposed coatings may be successively formed on said workpiece, andmeans sealed through said enclosure for selectively effectingregistration of diiferent portions of said workpiece with said aperturesand for selectively positioning said movable mask.

4. Apparatus for successively forming juxtaposed as well as superimposedlayers of difierent materials on a surface of a workpiece, saidapparatus comprising an enclosure, means for successively evaporating atleast two different coating forming materials mounted in said enclosure,a base supported above said evaporating means, a mask defining aplurality of juxtaposed apertures sup ported on said base, a second maskhaving at least one aperture formed therein and supported on said base,means for selectively moving one of said masks with respect to theother, a framework supported on said base on the side of said masks awayfrom said evaporating means, said framework having a guideway formedtherein, a workpiece holder for receiving a workpiece slideable in saidguideway and supported by said framework, means for selectively movingsaid holder in said guideway and successively registering differentportions of said workpiece with said apertures, and means sealed throughsaid enclosure for effecting successive relative movement of said masksand said workpiece holder, whereby diiferent portions of a workpiecemounted in said holder may be successively registered with saidapertures.

5. Apparatus for successively forming juxtaposed as well as superimposedlayers of difierent materials on a surface of a workpiece, saidapparatus comprising an enclosure, means for successively evaporating atleast two difierent coating forming materials mounted in said enclosure,a base supported above said evaporating means. a mask comprising aplurality of closely spaced parallel wires defining a plurality ofjuxtaposed apertures and supported on said base, a framework supportedon said base and having a guideway formed therein, a workpiece holderfor receiving a workpiece and movably mounted in said guideway, saidmask being positioned intermediate said workpiece holder and saidevaporating means, a second mask intermediate said workpiece holder andsaid evaporating means, said second mask having at least one apertureformed therein and being movably mounted on said base, adjustable meanson said framework for adjusting the spacing between said holder and saidmasks and for successively registering different portions of saidworkpiece with said apertures, and means sealed through said enclosurefor selectively positioning said movable mask and said workpiece holder.

6. Apparatus for successively forming juxtaposed as well as superimposedlayers of different materials on a surface of a workpiece, saidapparatus comprising an enclosure, means for successively evaporating atleast two different coating forming materials mounted in said enclosure,a base supported above said evaporating means, a mask comprising aplurality of closely spaced parallel wires defining a plurality ofjuxtaposed apertures and supported on said base, a framework supportedon said base and having a guideway formed therein, said guidewayextending transversely of said wires, a workpiece holder for receiving aworkpiece and movably mounted in said guideway, said mask beingpositioned intermediate said workpiece holder and said evaporatingmeans, a second mask intermediate said workpiece holder and saidevaporating means, said second mask having at least one aperture formedtherein and being movably mounted on said base for movement transverselyof said guideway, adjustable means on said framework for adjusting thespacing between said holder and said masks and for successivelyregistering different portions of said workpiece with said apertures,and means sealed through said enclosure for selectively positioning saidmovable mask and said workpiece holder.

7. The combination of apparatus for successively forming juxtaposed aswell as superimposed light permeable layers of different materials on alight permeable workpiece with means for determining the thickness ofsaid layers, said means comprising means for projecting a beam of lightthrough an aperture in an apertured mask and through portions of saidworkpiece while a layer is being formed through said aperture and onsaid portions, and means responsive to the amount of light fallingthereon positioned to receive light transmitted through said workpiece,the amount of light falling on said last mentioned means being afunction of the thickness of said layers.

8. The combination of apparatus for successively forming juxtaposed aswell as superimposed light permeable layers of different materials on alight permeable workpiece, the amount of light transmitted through saidlayers being a function of the thickness of said layers; said meansincluding means for projecting a beam of light through an aperture in anapertured mask only through those portions of said workpiece on which alayer is being formed through said aperture, light sensitive means formeasuring the amount of light received thereat and positioned to receivelight transmitted through said portions of the workpiece, and meansinterposed between said workpiece and said light sensitive means forrestricting the light received by said light sensitive means to that ofa predetermined wavelength or band of wavelengths.

9. Apparatus for successively forming juxtaposed as well as superimposedlayers of different materials on a surface of a workpiece, saidapparatus comprising an enclosure, means for successively evaporating atleast two different coating forming materials mounted in said enclosure,means including a guideway for movably supporting a workpiece inposition to receive said materials on the surface thereof, a maskdefining a plurality of juxtaposed apertures supported intermediate saidevaporating means and said workpiece, means for successively registeringdifferent portions of said workpiece with said apertures, wherebyjuxtaposed coatings may be successively formed on said workpiece, meanssealed through said enclosure for selectively effecting registrationvofdifferent portions of said workpiece with said apertures, means forprojecting light through said portions of the workpiece in registrationwith said apertures, light sensitive means for measuring the amount oflight received thereat and positioned to receive light transmittedthrough said portions of the workpiece, whereby the amount of lightreceived at said light sensitive means is a function of the thickness ofthe layers being formed.

10. Apparatus for successively forming juxtaposed as well assuperimposed layers of different materials on a surface of a workpiece,said apparatus comprising an enclosure, means for successivelyevaporating at least two different coating forming materials mounted insaid enclosure, means including a guideway for movably supporting aworkpiece in position to receive said materials on the surface thereof,a mask defining a plurality of juxtaposed apertures supportedintermediate said evaporating means and said workpiece, means forsuccessively registering different portions of said workpiece with saidapertures, whereby juxtaposed coatings may be successively formed onsaid workpiece, means sealed through said enclosure for selectivelyetfecting registration of different portions of said workpiece with saidapertures, means for projecting light through said portions of theworkpiece in registration with said apertures, light sensitive means formeasuring the amount of light received thereat and positioned to receivelight transmitted through said portions of the workpiece, whereby theamount of light received at said light sensitive means is a function ofthe thickness of the layers being formed, and means interposed betweensaid workpiece and said light sensitive means for restricting the lightreceived by said light sensitive means to that of a predeterminedwavelength or band of Wavelengths.

11. Apparatus for forming juxtaposed as well as superimposed coatings ona surface of a workpiece, said apparatus comprising a base, a frameworkremovably mounted on said base, at least one mask on said base andincluding elements defining apertures through which material may travelto form layers on said surface, a holder movably mounted on saidframework said holder supporting said workpiece in registration withsaid apertures, and adjustable means for selectively positioning saidholder in close spaced relation with said mask.

12. Apparatus for forming juxtaposed as well as superimposed coatings ona surface of a workpiece, said apparatus comprising a base, a maskconnected to said base, a plurality of elements on said mask anddefining a plurality of juxtaposed apertures, a movable mask having atleast one aperture formed therein and movably mounted on said base, aframework removably mounted on said base, a workpiece holder movablymounted on said framework and supporting the workpiece in registrationwith said apertures, and adjustable positioning means for selectivelymoving said holder in close spaced relation with said first mentionedmask and for selectively positioning said movable mask.

13. Apparatus for forming juxtaposed as well as superimposed coatings ona surface of a workpiece, said apparatus comprising a base, a pair ofspaced apart members connected to said base, a plurality of alined wiresstretched between and connected to said members, said wires defining aplurality of apertures, said'base having a guideway formed therein, amovable mask slideably mounted in said guideway and having at least oneaperture formed therein, a framework removably mounted on said base andhaving a guideway formed therein, a holder slideably mounted in theguideway of said framework and for supporting a workpiece inregistration with said apertures, adjustable means for selectivelypositioning said holder in close space relation with said wires, andmeans for selectively positioning said movable mask in registration withsaid holder and said wires.

14. The method of forming juxtaposed interference color filters on alight permeable workpiece with a set of filters of one color interlacedwith a set of another color and each capable of transmitting a differentpredetermined spectral bandwidth, said method including the steps ofmasking all but those spaced apart portions of the work piece on whichthe set of filters of one color are to be 13 formed, then forming onsaid portions successive superimposed layers of high and low index ofrefraction material each of a thickness determined by exposing saidportions only to light and measuring the amount of light of a givenwavelength transmitted through said portions to form said interferencecolor filter set.

15. The method of forming juxtaposed interference color filters on alight permeable workpiece with a set of filters of one color interlacedwith a set of another color and each capable of transmitting a differentpredetermined spectral bandwidth, said method comprising the steps ofmasking all but those spaced apart portions of the workpiece on whichthe set of filters of one color are to be formed, then forming on saidportions successive superimposed layers of high and low index ofrefraction material each of a thickness determined by exposing saidportions only to light and measuring the amount of light of a givenwavelength transmitted through said portions to form said color filterset, then masking all but other portions of the workpiece on whichanother set of interference filters of a different color are to beformed, and then forming on said portions successive superimposed layersof high and low index of refraction material each of a thicknessdetermined by exposing said other portions only to light and measuringthe amount of light of a different g'ven wavelength transmitted throughsaid other portions to form another set of interference filters.

16. The method of forming juxtaposed interference color filters on alight permeable workpiece with a set of filters of one color interlacedwith a set of another color and each capable of transmitting a differentpredetermined spectral bandwidth, said method comprising the steps ofmasking all but those spaced apart portions of the workpiece on whichthe set of filters of one color are to be formed, then forming on saidportions successive superimposed layers of high and low index ofrefraction material each of an optical thickness of substantially or anodd multiple of a A wavelength of light of a given wavelength, saidthickness being determined by exposing said portions only to light andmeasuring the amount of light of said given wavelength transmittedthrough said portions to form said color filter set, then masking allbut other portions of the workpiece on which another set of interferencefilters of a different color are to be formed, and then forming on saidportions successive superimposed layers of high and low index ofrefraction material each of an optical thickness of substantially or anodd multiple of wavelength of light of a different given wavelength,said thickness being determined by exposing said other portions only tolight and measuring the amount of light of said different wavelengthtransmitted through said other portions to form another set ofinterference filters.

17. The method of manufacturing a ray sensitive target for a cathode raytube having juxtaposed color filters with a set of filters of one colorinterlaced with a set of another color and each capable of transmittinga difierent predetermined spectral bandwidth and having for each filtera transparent conductive signal strip which is electrically coupled tothe ray sensitive material, said method including the steps of maskingall but those spaced apart portions of the target on which the set offilters of one color are to be formed, evaporating onto said portionsmaterial to form one set of color filters capable of transmitting apredetermined spectral bandwidth, and evaporating onto said portionsmaterial to form transparent conductive signal strips.

18. The method of manufacturing a ray sensitive target for a cathode raytube having juxtaposed interference color filters with a set of filtersof one color interlaced with a set of another color and each capable oftransmitting a different predetermined spectral bandwidth and having foreach filter a transparent conductive signal strip which is electricallycoupled to the ray sensitive material, said method including the stepsof masking all but those spaced apart portions of the workpiece on whichthe set of filters of one color are to be formed, then forming on saidportions successive superimposed layers of high and low index ofrefraction material each of a thickness determined by exposing saidportions only to light and measuring the amount of light of a givenwavelength transmitted through said portions to form said interferencecolor set, and forming on each of said thus formed filters a layer oftransparent conductive material.

References Cited in the file of this patent UNITED STATES PATENTS2,418,627 Dimmick Apr. 8, 1947 2,432,950 Turner et al. Dec. 16, 19472,433,635 Sukumlyn Dec. 30, 1947 2,472,605 McRae et a1 June 7, 19492,545,576 Godley Mar. 20, 1951 2,600,579 Ruedy et al June 17, 1952

14. THE METHOD OF FORMING JUXTAPOSED INTERFERENCE COLOR FILTERS ON ALIGHT PERMEABLE WORKPIECE A SET OF FILTERS OF ONE COLOR INTERLACED WITHA SET OF ANOTHER COLOR AND EACH CAPABLE OF TRANSMITTING A DIFFERENTPREDETERMINED SPECTRAL BANDWIDTH, SAID METHOD INCLUDING THE STEPS OFMASKING ALL BUT THOSE SPACED APART PORTIONS OF THE WORKPIECE ON WHICHTHE SET OF FILTERS OF ONE COLOR ARE TO BE FORMED, THEN FORMING ON SAIDPORTIONS SUCCESSIVE SUPER-